Working memory (WM) can be defined as the amount of information that can be held in the mind and manipulated in order to allow the completion of a mental task such as comprehension, problem-solving, or serial recall. WM often is measured with tasks that require the storage and processing of information at the same tome. Past research shows that individual and developmental differences in WM are important for such complex cognitive tasks, but it is not yet clear what basic processes underlie WM measures and their developmental change. This revised competing continuation proposal adapts methods that we have devised recently to observe developmental changes in serval basic processing parameters, from age 6 to adulthood: the short-term memory retrial rate for recently presented information, speeded articulation rates; the persistence of automatically held information, such as sensory memory; and the capacity of S.T.M., measured in unrelated chunks of information. The observations of developmental changes in these parameters are important because many researchers have suggested that most of these basic parameters (analogous to computer hardware) stay fixed, and that is primarily knowledge and strategies (analogous to computer software) that change with development in childhood. Rather than just accumulating further support for developmental changes in the basic parameters, the planned research has three other specific aims. (1) The first aim is to understand the mechanisms of the basic parameters within information processing system. For example, one study examines whether the capacity limits are central limits in the attentional focus as expected, or instead are capacity limits in modality-specific stores ( e.g., separate capacity limits for auditory/verbal and visual/spatial stimuli). (2) the second aim is to learn how the basic parameters influence one another. For example, one study examines whether the developmental change in retrial rates could be an indirect consequence of the change in capacity limits, by imposing a memory load during the measure of retrieval rates. (3) The third aim is to learn how the basic parameters are related to more complex measures of information processing ability, as well as to one another. This will be investigated in relatively large correlational study and with models incorporating the basic parameters, complex as well as simple memory spans, and measures of aptitude and scholastic achievement. This theoretical advance also should help in understanding various learning and language disorders, which are known to be marked by poor memory span for theoretical reasons that need clarification.